Bible Costumes Start with a flat twin sheet. Mine was about 86 by 62 inches. Make an armhole slash about 20 inches from each side and about 12-18 inches deep. Narrow hem the armhole openings. Make a dart at the bottom to keep the fabric from tearing. Fold the armhole section back and seam the shoulders. I allowed 6 inches extra neck space on the back of the costume. The finished garment is about 50 inches long--use any extra cloth from the bottom to make a sash.